This invention relates generally to conveyor diverting systems, and, more particularly, to conveyor diverting systems having an endless conveying surface composed of multiple surface members, each one or group of adjacent ones mounted with a laterally movable shoe capable of diverting articles from the conveyor by pushing laterally against the articles as they move down the conveyor. Such lateral pushing thereby diverts a package, such as from the main conveyor to an adjacent branch conveyor, or other receiving structure.
Conveyor diverting systems using a moving conveying surface consisting of a plurality of parallel surface members, the conveying surface being propelled, such as by being mounted to endless chains, have been known for a number of years. Such diverting systems utilize a diverter shoe movably mounted on one or more surface members for lateral movement with respect to the conveying surface under the guidance of a track network. The track network is located generally under the conveying surface and guides the diverter shoes via pins descending from the diverter shoes and engaging the track network. Diverters in the track network selectively transfer guidance of each diverter shoe from a track running in the direction of the movement of the conveying surface to a diagonal track, or plurality of diagonal tracks, in order to cause lateral movement of the diverter shoes. An example of a diverting gate used to selectively transfer guidance of diverter shoes between tracks is disclosed in U.S. Pat. No. 5,409,095, issued to Hoshi et al., and U.S. Pat. No. 5,039,912, issued to Cotter. In order to avoid wasted spacing between variable-length packages, such diverting systems may include manual or automatic measuring means at an infeed point to cause the diverter gate associated with the selected branch conveyor to divert a selected number of shoes corresponding in general to the length of the package. Exemplary of this type of conveyor are U.S. Pat. No. 3,361,247, issued to James N. Lauzon et al. and U.S. Pat. No. 4,738,347, issued to Brouwer, and commonly assigned with the present invention.
With increased demands for the number of packages to be conveyed by such conveying systems, the inter-package spacing distance has become a critical factor in the design of conveying systems. Decreasing the spacing between packages on the conveyor allows a greater throughput of packages by the conveyor. Conversely, providing more space between the packages results in a diminished efficiency and throughput.
A specific minimum inter-package spacing is required in this system as a result of the rotation of the diverted package as it is initially diverted. Because of this rotation, additional inter-package spacing is required to avoid conflict between the diverting package and a closely trailing package. This rotation pushes the trailing corner of the package adjacent the branch conveyor back a distance, which can be estimated using the width (W) of the package and the acute angle (xcex8) which is formed by the intersection of the material flow on the main conveyor and the diverter shoe diagonal guide track. Using these two variables and assuming that the package rotates about the trailing corner opposite the branch conveyors, it will be observed that:
A=W sin xcex8
where A is the distance the trailing corner adjacent the branch conveyor is pushed back by the package""s rotation. It is, therefore, necessary with this system that packages to be diverted are not spaced closer together than the distance W sin xcex8.
By way of example, if a diverting branch is oriented at about 20xc2x0 with packages 16 inches in width, an inter package distance of approximately 5.5 inches is necessary. If the package is 24 inches long, this results in the need for approximately 23% more empty space on the conveyor. A hypothetical system that could divert packages without any significant space between packages could thus produce a 23% increase in package throughput without any increase in conveyor speed. The high desirability of such a system is thus clear.
Prior methods of diverting packages that addresses the problem of reducing the required inter-package spacing, is described in commonly assigned U.S. Pat. No. 5,165,515, issued to Michael L. Nitschke et al., which is commonly assigned with the present application. This system increases throughput by not rotating the diverted packages. This non-rotation is accomplished by using a plurality of generally parallel diverting tracks oriented diagonally with respect to the direction of conveyor movement, instead of a single diverting track. Each track has its own diverting gate which is actuated to divert the movement of the diverting shoes from the direction of the conveyor to the lateral diverting direction. By simultaneously activating more than a single diverting gate, a group of diverting shoes corresponding to the measured package length can be moved laterally across the conveyor surface. This group of shoes acts along nearly the entire length of the package to be diverted and, therefore, causes no rotation of the package. Without rotation of the package, the inter-package spacing requirement is reduced to a minimum.
However, this technique is not without difficulties. The deliberate non-rotation of the packages means the packages will enter the branch conveyor still aligned parallel to the main conveyor, but oriented generally diagonally with respect to the branch conveyor (i.e., their lengthwise sides are not parallel to the direction of motion of the branch conveyor). This orientation significantly increases the necessary width of the branch conveyors, resulting in an increase in cost and a reduction in the spacing on branch conveyors.
Still another method of diverting packages which reduces the required inter-package spacing, is described in commonly assigned U.S. Pat. No. 5,927,465, issued to Shearer, Jr. With this system, an automatic controller oversees the operation of the diverting gates to determine which diverting gates are to be actuated and for how long, depending upon the measured length of the packages on the conveyor. Once the length of the package is determined, the controller determines whether a package will be diverted using one diverting gate or two (or more) diverting gates. For certain situations, such as long packages, a single diverter is activated and as many diverting shoes are diverted as necessary to divert the package through the single diverting gate. Packages diverted in this manner are rotated, with the trailing corner of the package moving in an initial rearward direction.
Other packages are diverted with two or more gates in a manner that the packages are initially diverted out of line with other packages without substantially rotating the packages, in the same manner as in Nitschke et al. ""515 Patent. After the initial diverting, the package is then rotated prior to discharge to the spur. This has the advantage of the Nitschke et al. ""515 Patent of not requiring increased gaps between packages but eliminates the disadvantage of increased spur size. However, some of the packages, such as long packages, are still diverted using conventional techniques and increased gaps must be provided at both ends of such packages.
It will thus be observed that there exists a need for a conveyor diverting system that can divert packages with little or no inter-package spacing, and ensure that packages diverted to the branch conveyor are properly aligned, all while keeping costs to a minimum.
The present invention provides a sortation conveyor which achieves efficiency gains through reduction of the inter-package spacing. These efficiency gains are especially desirable because they can be achieved without the extra power consumption, noise, and wear that results from increasing the conveyor speed. The present invention increases conveyor diverting system throughput by utilizing a diverting track network having at least one downstream diverting track and a plurality of upstream diverting tracks. The tracks are configured to enable movable pushers to initially divert a package in an orientation which prohibits the article being diverted from interfering with the trailing article.
According to one aspect of the invention, a conveyor system includes a conveyor surface having a direction of travel, which conveys articles substantially in a line. Movable pushers are mounted on the conveying surface and are adapted to move transversely thereacross. A diverting track network, positioned beneath the conveying surface, is configured to move at least two movable pushers substantially perpendicular to the direction of travel of the conveying surface for at least an initial distance, and thereafter to guide the movable pushers in a direction which causes the rotation of at least some of the articles being diverted after being placed out of line with the other articles. The ability of the diverting track network to initially move an article from the line of articles in a direction substantially perpendicular to the direction of travel of the conveying surface, and thereafter subsequently rotate at least some of the articles being diverted enables the minimization of space between articles, and hence increases throughput.
According to another aspect of the invention, a conveyor system for diverting articles includes a conveying surface moving in a particular direction, and at least one branch conveyor extending from the conveying surface. A plurality of diverters are mounted on the conveying surface and are movable between a diverting state and a non-diverting state, while a plurality of movable pushers, mounted on the conveying surface, are movable across the conveying surface when a particular diverter is in the diverting state. A control system is configured to determine the length of articles conveyed, and is connected to a diverting system having at least one downstream diverting track extending substantially across the conveying surface, and a plurality of upstream diverting tracks which each extend partially across the conveying surface. The diverting system simultaneously diverts at least one movable pusher along the downstream diverting track when the leading end of the article to be diverted is positioned thereover, and at least one movable pusher along an upstream diverting track, proximate to the trailing end of the article. Simultaneously actuating at least a pair of movable pushers to engage an article to be diverted, proximate to both its leading end and trailing end, assures effective diversion of articles from the conveying surface.
According to yet another aspect of the invention, a conveyor system for converting articles includes an array of movable surface members defining a conveying surface, and a plurality of diverting shoes mounted on the surface members. A guide track is positioned below the surface members and adapted to guide the diverting shoes. A plurality of diverters are positioned along and interrupt the guide track, and assume either a non-diverting state or a diverting state. When in the non-diverting state, the diverting shoes move along the guide track uninterrupted, while in the diverting state, the diverting shoes are diverted from the guide track. A diverting track network, positioned underneath the conveying surface, meets the diverters, and includes at least one downstream diverting track extending substantially across the conveying surface and a plurality of upstream diverting tracks, each of which extends partially across the conveying surface. A controller, in operational connection with at least one sensor, simultaneously actuates a first diverter to divert a diverting shoe along the downstream diverting track when the first diverter is proximate to the leading end of the article, and a second diverter proximate to the trailing end of the article. Actuating a first diverter farthest downstream, and proximate to the leading end of the article and a second diverter upstream and proximate to the trailing end of the article effectively enables the diversion of articles onto a branch conveyor.
The present invention also advances a method for diverting articles which includes the steps of conveying articles substantially in a line with the conveying surface, and applying a perpendicular force component to substantially all the articles to be diverted. The perpendicular force component is substantially perpendicular to the direction of conveyor motion and diverts the article initially out of line with the other articles traveling along the conveying surface. The perpendicular force component is then altered for at least some of the articles after the article is diverted out of line, by including a rotational force component during a subsequent portion of the diverting motion. Initially diverting an article out of a line of articles, and subsequently rotating the article after it has been diverted from the line, permits the spacing between articles to be minimized, and therefore enhances the efficiency and throughput of the conveyor system.
According to yet another aspect of the invention, a method for diverting articles includes measuring the length of the articles conveyed along the conveying surface, and providing a diverting track network positioned beneath the conveying surface which includes at least one downstream diverting track laterally traversing substantially the entire conveying surface, and a plurality of upstream tracks partially laterally traversing the conveying surface. A plurality of diverters are provided which cause the movable pushers to move along the associated track, at least partially across the conveying surface when a diverter is activated to a diverting state. The method also includes simultaneously activating at least two of the diverters wherein one of the diverters is associated with the downstream diverting track and positioned proximate to the leading end of the article, and the other diverter is positioned proximate to the trailing end of the article. Diverting articles from a conveying surface by activating at least two diverters wherein one diverter, associated with the downstream track, is actuated when the leading end of the article is positioned thereover, and the other diverter is proximate to the trailing end of the article provides an efficient method for diverting articles onto a secondary conveying surface.